Estimation of Standing Stock and Decomposition Rates of Labile Organic Matter in Waters of Novorossiisk Bay,Black Sea

The annual dynamics of the decomposition rate, standing stock, and residence time of labile organic matter as an index of full self-purification were investigated in Novorossiisk Bay, Black Sea. The results are suggestive of fairly effective processes of biological self-purification in polluted waters of the bay. The decomposition rate was highest (0.3–0.7 mgO₂/l per day) during the summer, and it decreased by 4–8 times in winter. The residence time of labile organic matter was 97–104 days in winter and 8–11 days in summer. Oxygen consumption rates measured in different areas of the bay conformed to their trophic status and were not above the normal level for summer.     

Rapid evolution of novel traits in microorganisms

The use of natural microorganisms in biotransformations is frequently constrained by their limited tolerance to the high concentrations of metabolites and solvents required for effective industrial production. In many cases, more robust strains have to be generated by random mutagenesis and selection. This process of directed evolution can be accelerated in mutator strains, which carry defects in one or more of their DNA repair genes. However, in order to use mutator strains, it is essential to restore the normal low mutation rate of the selected organisms immediately after selection to prevent the accumulation of undesirable spontaneous mutations. To enable this process, we constructed temperature-sensitive plasmids that temporarily increase the mutation frequency of their hosts by 20- to 4,000-fold. Under appropriate selection pressure, microorganisms transformed with mutator plasmids can be quickly evolved to exhibit new, complex traits. By using this approach, we were able to increase the tolerance of three bacterial strains to dimethylformamide by 10 to 20 g/liter during only two subsequent transfers. Subsequently, the evolved strains were returned to their normal low mutation rate by curing the cells of the mutator plasmids. Our results demonstrate a new and efficient method for rapid strain improvement based on in vivo mutagenesis.     

Taxonomic composition and interannual variations in numerical density of meroplankton in the Sea of Azov

This paper presents data on the taxonomic composition and dynamics of numerical density of meroplankton in the Sea of Azov. Studies performed in June 2003–2005 revealed benthic invertebrate larvae of 26 taxa: Polychaeta, 7; Cirripedia, 1; Decapoda, 5; Gastropoda, 5; and Bivalvia, 8. Meroplankton was dominated by larvae of species that are able to endure considerable concentrations of pollution by labile sulfides in bottom sediments and eutrophication: Mytilaster lineatus, Cerastoderma sp., Abra ovata (Philippi), Hydrobia acuta (Gastropoda), and Amphibalanus improvisus (Cirripedia). The spatial and temporal variations in the structure of dominant species and numerical abundance of meroplankton in the Sea of Azov are likely to be associated with water temperature fluctuations, pelagic predators, and eutrophication. Under anthropogenic stress and predation pressure, most larvae of benthic invertebrates are apparently unable to complete metamorphosis and contribute to recruitment to parental populations. Thus, the numerical density of meroplankton in the Sea of Azov can significantly vary, even over one month.     

Bioluminescent sensors for detection of bioavailable Hg(II) in the environment.

Biosensors for the detection of pollutants in the environment can complement analytical methods by distinguishing bioavailable from inert, unavailable forms of contaminants. By using fusions of the well-understood Tn21 mercury resistance operon (mer) with promoterless luxCDABE from Vibrio fischeri, we have constructed and tested three biosensors for Hg(II). Bioluminescence specified by pRB28, carrying merRo/pT, by pOS14, mediating active transport of Hg(II), and by pOS15, containing an intact mer operon, was measured in rich and minimal media. The highest sensitivities were achieved in minimal medium and were 1, 0.5, and 25 nM Hg(II) for pRB28, pOS14, and pOS15, respectively. The utility of the biosensors in natural waters was demonstrated with freshwater, rain, and estuarine samples supplemented with Hg(II). mer-lux carried by pRB28 and pOS14 responded to Hg(II) in mercury-contaminated water samples collected from a freshwater pond. Semiquantitative analyses based on light emission in samples collected from the inlet (analytically determined total mercury, approximately 20 nM) and outlet (total mercury, approximately 7 nM) of the pond showed bioavailable mercury at approximately 20 and 1 to 2 nM, respectively. Thus, the biosensors described here semiquantitatively detect bioavailable inorganic mercury (at a nanomolar to micromolar concentration range) in contaminated waters.     

Use of an ipb-lux Fusion To Study Regulation of the Isopropylbenzene Catabolism Operon of Pseudomonas putida RE204 and To Detect Hydrophobic Pollutants in the Environment

A DNA segment involved in the regulation of the isopropylbenzene (cumene) catabolism operon (ipb) of plasmid pRE4 from Pseudomonas putida RE204 and the Vibrio fischeri luciferase genes, luxCDABE, were used to create an ipbRo/pA(prm1)-luxCDABE reporter fusion plasmid, pOS25. Escherichia coli HMS174(pOS25) produces light in the presence of inducers of the ipb operon. These inducers were shown to be hydrophobic compounds and to include monoalkylbenzenes, substituted benzenes and toluenes, some alkanes and cycloalkanes, chlorinated solvents, and naphthalenes. Complex hydrocarbon mixtures, such as gasoline, diesel fuel, jet fuels (JP-4 and JP-5), and creosote, were also inducers of ipb-lux. Bacteria carrying the ipb-lux reporter may be useful as bioindicators of hydrocarbon pollution in the environment and may be particularly valuable for examining the bioavailability of inducing pollutants.     

Role of Na+ in transport of Hg2+ and induction of the Tn21 mer operon.

The effects of sodium ions on the uptake of Hg2+ and induction of the Tn21 mer operon were studied by using Escherichia coli HMS174 harboring the reporter plasmids pRB28 and pOS14. Plasmid pRB28 carries merRT', and pOS14 carries merRTPC of the mer operon, both cloned upstream of a promoterless luciferase gene cassette in pUCD615. The bioluminescent response to 1 microM Hg2+ was significantly inhibited in E. coli HMS174(pRB28) in minimal medium supplemented with sodium ions at 10 to 140 mM. After initial acceleration, light emission declined at 50 nM Hg2+ in the presence of Na+. The mer-lux assay with resting cells carrying pRB28 and 203Hg2+ uptake experiments showed increased induction and enhanced mercury uptake, respectively, in media supplemented with sodium ions. The presence of Na+ facilitated maintenance of bioluminescence in resting HMS174(pRB28) cells induced with 50 nM Hg2+. External K+ stimulated bioluminescent response in HMS174(pRB28) and HMS174(pOS14) grown in sodium phosphate minimal medium devoid of potassium ions. Sodium ions appear to facilitate mercury transport. We propose that sodium-coupled transport of mercuric ions can be one of the mechanisms for mercury uptake by E. coli and that the Na+ gradient may energize the transport of Hg2+.     

Seasonal dynamics of micro- and mesoplankton of the Temryuk estuarial pelagic ecosystem of the Sea of Azov

The variability in the composition and dynamics of microplankton (ciliate) and mesoplankton in the Temryuk estuarial pelagic ecosystem has been studied at different stages of succession of the pelagic communities. Invertebrates of 54 taxa, including ciliates of 24 taxa, have been identified. Among the ciliates, Myrionecta rubra, Mesodinium pulex, Halteria grandinella, Strombidium conicoides, S. sp. 1, S. sp. 2, Strobilidium sp., Loxmaniella oviformis, and Tintinnopsis minuta were dominant. The share of mesoplankton in the total biomass of zooplankton reached 70% (1.3 g/m³) and was estimated as the maximal value for mesoplankton of the Sea of Azov. Marine and brackish-water rotifers of the genus Synchaeta and Asplanchna priodonta constituted 55% of the biomass. The most abundant meroplanktonic larvae of Amphibalanus improvisus amounted to 30% of the total mesoplankton biomass. In the seasonal dynamics of microplankton development, two peaks of the biomass were revealed: spring (0.45 g/m³) and more expressed summer (0.9 g/m³); in mesoplankton there was one spring peak (3.7 g/m³). Superdense communities of ciliates and detritophages in some periods of the vegetative season are typical for the hypereutrophic ecosystem and can testify to the catastrophic character of its transformation.     

Ichthyoplankton of the coastal waters of northeastern shelf of the Black Sea and the Kerch Strait

We study the state of summer ichthyoplankton and dynamics of its taxonomic composition and abundance near large harbor cities (Novorossiysk and Tuapse), as well as in the navigation areas and near transshipment harbor facilities (Taman?? Prichernomor??e and Kerch Strait). We show that temporal-spatial changes in the taxonomic composition and abundance of ichthyoplankton are determined by fluctuations of water temperature, pressure of predatory comb jelly Mnemiopsis leydyi and level of water pollution. High mortality rate and low abundance of fish eggs and larvae in the polluted areas of Novorossiysk, Tuapse, and Kerch Strait indicate unfavorable conditions for the embryonic and postembryonic development of fish in these areas. As judged by the state of ichthyoplankton the most favorable conditions are in the open part of the Novorossiysk Bay and Taman?? Prichernomor??e. Starting from 2002, the spawning populations of pelagophylic fish in the Novorossiysk Bay are gradually recovering to the level of 1980.     

Functioning of the Sea of Azov ecosystem

The structure and functioning of the Sea of Azov ecosystem have been studied. Based on the results of an analysis of the principal community components (phytoplankton, bacterioplankton, zooplankton, macrozoobenthos, and fish), the elements of balance equality and food utilization by the ecosystem components were calculated and schemes of their energy flow were constructed. The intensity and trends of production-destruction processes were characterized. It was revealed that the main energy flow in the Sea of Azov ecosystem passes through the detritus food web (81%). Along with eutrophication and sulfide pollution of bottom sediments, the impact of predatory ctenophore Mnemiopsis leidyi (A. Agassiz) determines to a considerable extent the pattern of the ecosystem’s transformation.